Process for manufacturing unsaturated polyester resins

ABSTRACT

In a process for manufacturing unsaturated polyester resins which comprises (A) a stage of reacting a dialkyl terephthalate with a polyhydric alcohol in the presence of an interesterification catalyst, (B) a stage of reacting the reaction product obtained at the stage (A) with an unsaturated dicarboxylic acid, one or more polyhydric alcohols and optionally a saturated dicarboxylic acid to produce an unsaturated alkyd resin and (C) a stage of dissolving the unsaturated alkyd resin obtained at the stage (B) in a vinyl monomer, the reaction at the stage (A) or (B) is carried out in the coexistence of a hydroquinone and a phosphite.

United States Patent Watanabe et al. Aug. 26, 1975 [54] PROCESS FQR MANUFACTURING 3 l96.l3l 7/[965 Mayer et al 4 a t t 260/75 UNSATURATED POLYESTER RES'NS 1252.94] 5/l966 Mayer Et al t l l i a a 260/75 1345339 10/1967 Parker et al. 260/75 1 Inventors: Takeyoshi Watanflbe: Morimasa 1361.846 1/1968 Glcim et al. a a u a v H 260/860 Sato; Wataru Koga, all of Hitachi, 3 4(l4 l2l [0/1968 Barkcy 260/457 Japan 3,427,267 2/!96'9 Sticgcr et al a a t 4 4 260/22 3,483,!51 l2/l969 Biarnais et al, 260/22 [73] Assignee: Director-General (Mr. Keishin Mfltsumow) Agency of Industrial Primary Examiner-Mclvin Goldstein Sc'ence & Technology Tokyo Japan Assistant Examiner-E. A. Nielsen 22 Fi Aug 30 1973 Attorney, Agent, or FirmWilliam J. Daniel [n a process for manufacturing unsaturated polyester [30] Foreign Application Priority Data resins which comprises (A) a stage of reacting a dial- Aug. 31. I972 Japan 4. 4186603 y terephlhalate with a P y y alcohol in presence of an intcresterification catalyst (B) a stage (52] US. Cl. 260/865; 260/75 P; 260/75 UA; of reacting the reaction product obtained at the stage 260/36} (A) with an unsaturated dicarboxylic acid one or [5 l] Int. Cl. H C08! 2l/00: COSg l7/l0; C08g 51/58 more polyhydric alcohols and optionally a saturated sx Field of Search u, 260/86l. 865. 75 P, 75 UA diwrhoxylic acid 10 producc an unsaturated alkyd resin and (C) a stage of dissolving the unsaturated [56] References (ji d alkyd resin obtained at the stage (B) in a vinyl mono UNITED STATES PATENTS mer, the reaction at the stage (A) or (B) is carried out in the coexistence of a hydroquinone and a phosphite. 2.904.533 9/1959 (arlston et al. w. 260/75 3.042.650 7/l962 Bockstahlcr 260/86l 9 Claims, No Drawings PROCESS FOR MANUFACTURING UNSATURATED POLYESTER RESINS BACKGROUND OF THE INVENTION This invention relates to an improvement in the proccss for manufacturing unsaturated polyester resins. More particularly. this invention relates to an improved process for manufacturing from a dialkyl terephthalatc, unsaturated polyester resins which are excellent in mechanical properties and corrosion resistance.

As a general process for manufacturing unsaturated polyester resins, there is known a process wherein an aromatic dicarboxylic acid such as phthalic acid or phthalic anhydride is reacted with one or more polyhydric alcohols plus an unsaturated dicarboxylic acid and the resulting reaction product is dissolved in a vinyl monomer. In this process, the use ofisophthalic acid in place of the phthalic acid or phthalic anhydride for the purpose ofimproving mechanical properties and corrosion resistance of the end product, ie. the cured product ofthe unsaturated polyester resin, is already known (E. E. Parker, Ind., Eng, Chem., 58(4), 53 H966). However, the cured product of an unsaturated polyester resin obtained from isophthalic acid as aromatic dicarboxylic acid component also fails to possess practically satisfactory mechanical properties and corrosion resistance. It is expected that mechanical properties and corrosion resistance of the resin would be improved if in this process dimethyl tercphthalate were substituted in place of isophthalic acid. As a polyester derived from dimethyl terephthalate tends to be crystalline, the reaction should be conducted for a long period of time at a sufficiently high temperature. If the extent of reaction is insufficient, the polyester is small in yield and easily tends to crystallinity. Moreover. mechanical properties and corrosion resistance become inferior. This process, moreover. has a fatal drawback; mainly, it requires a high temperature and along period of time for the reaction between dimethyl terephthalate and one or more polyhydrie alcohols so that the resin is obtained only in agelled or almost gelled form in extremely unstable state and thus unsuited for practical use.

Thus, a practical process for manufacturing unsaturated polyester resins using a terephthalic acid as the aromatic dicarboxylic acid component has not been known hitherto.

BRIEF SUMMARY OF THE INVENTION lt is, therefore, an object of this invention to provide unsaturated polyester resins possessing improved mechanical properties, corrosion resistance and crystallinity.

Another object of this invention is to provide stable unsaturated polyester resins derived from terephthalic acid as the aromatic dicarboxylic acid component.

Still another object of this invention is to provide a process for efficiently manufacturing unsaturated polyester resins ofgood quality which comprises bringing a dialkyl terephthalatc, one or more polyhydric alcohols, an unsaturated dicarboxylic acid and optionally a saturated dicarboxylic acid into reaction at two stages.

Other and further objects, features and advantages of this invention will appear more fully from the following description.

DETAILED DESCRlPTlON OF THE lNVENTlON In accordance with this invention, the aforementioned objects can be attained by a process comprising (A) a first stage of reacting a dialkyl terephthalate with a polyhydric alcohol in the presence of an interesterifi cation catalyst, (B) a second stage of reacting the reaction product of stage (A) with an unsaturated dicarboxylic acid, one or more polyhydric alcohols and optionally a saturated dicarboxylic acid to produce an unsaturated alkyd resin and (C) a third stage of dissolving the unsaturated alkyd resin obtained from stage (B) in a vinyl monomer, characterized by carrying out the reaction of stage (A) or (B) in the concurrent presence of a hydroquinone and a phosphite,

The term unsaturated dicarboxylic acid" is used herein to mean a dicarboxylic acid having an unsatu rated bond capable of reacting with a vinyl monomer, while the term "saturated dicarboxylic acid is used herein to mean a diearboxylic acid having no unsaturated bond capable of reacting with a vinyl monomer.

Terephthalic acid used in this invention as the aromatic dicarboxylic acid component has to be used in the form of a dialkyl ester thereof in which the alkyl moieties are each a lower alkyl group of at most 4 carbon atoms. This is because the free tcrephthalic acid does not react directly with a polyhydric alcohol even in the presence of an interesterification catalyst.

Examples of the unsaturated dicarboxylic acid used in this invention include maleic acid, maleic anhydride, fumaric acid, itaconic acid and the like. Examples of the saturated dicarboxylic acid used optionally in this invention include phthalic acid, phthalic anhydride, isophthalic acid, adipic acid, sebacic acid, tetrahydrophthalic acid, tctrahydrophthalic anhydride, methyl-tetrahydrophthalic acid, methyl-letrahydrophthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, endomethylene tetrahydrophthalic anhydride, ehlorcndic acid and the like.

On the other hand, examples of the polyhydric alcohol include ethylene glycol, dicthylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, neo pentyl glycol, isopentyl glycol, 1,6-hexanediol and the like.

The vinyl monomer to be mixed with the unsaturated alkyl resin obtained according to the reaction at the stages (A) and (B) of this invention is preferably styrene, vinyltoluene, tert-butylstyrcne, chlorostyrene and diallyl phthalate.

The interesterification catalyst used at the stage (A) ofthis invention is preferably lead acetate, zine acetate, lead oxide, manganese chloride, alcoholic manganese chloride, etc.

In the practice of this invention, it is indispensable to use a combination of a hydroquinone and a phosphite at stage (A) or (B). The use of only one of the two fails to achieve the desired effect. Examples of suitable hydroquinones include hydroquinone itself, 2,5-ditertbutylhydroquinone, hydroquinone ethers, bisphenols and resoreinol. Especially preferable are pdihydroxybenzcnes and their derivatives, Examples of the phosphite include monoalkyl phosphites such as monomethyl phosphite and monoethyl phosphite, dialkyl phosphites such as dimethyl phosphite and diethyl phosphite, trialkyl phosphites such as trimethyl phosphitc and triethyl phosphite, and phenyl phosphites such as diphenyl phosphitc, triphenyl phosphite and tri- 3 tnonylphenyl) phosphite. Especially preferable are trialkyl phosphitcs and triphenyl phosphites.

The use of too small amounts of the hydroquinone and the phosphites fails to attain satisfactory results. while the use of too large amounts tends to prolong the curing time in the curing treatment. Thus. a combina tion of the hydroquinone and the phosphite is employed in an amount within a critical range; the hydroquinone is used in an amount of 0.005 0.04% by weight. preferably 0.008 -0.027 by weight based on the total amount of the saturated and unsaturated dicarboxylic acids and the polyhydric alcohol. while the phosphite is used in an amount of 0.05 0.5% by weight. preferably 0.08 0.3% by weight.

In accordance with a preferable embodiment of this invention. a dialkyl terephthalatc. a polyhydric alcohol. a hydroquinone and a phosphite are first heated at 200-250C in the presence of an interesterification catalyst to effect the interesterification reaction. To the reaction product are then added an unsaturated diearboxylic acid. a polyhydric alcohol and optionally a saturated dicarboxylic acid. The resulting mixture is heated at l80-230C to effect condensation reaction and the product thus obtained is dissolved in a vinyl monomer. A stable, less colored unsaturated polyester resin possessing the desired viscosity. acid number and molecular weight is thus produced.

In accordance with another embodiment of this invention. reaction is carried out first between a dialkyl terephthalate and a polyhydric alcohol in the presence of an interesterification catalyst and then between the reaction product and newly added unsaturated dicar boxylic acid. one or more polyhydric alcohols. a hydroquinonc, a phosphite and optionally a saturated dicar boxylic acid and finally the reaction product thus obtained is dissolved in a vinyl monomerv An unsaturated polyester resin excellent in resistance to gelling and in stability during storage is obtained in this way. According to this embodiment. however. the coloration of the product is somewhat inferior as compared with the case of adding a hydroquinone and a phosphite at stage (A) in the first mentioned embodiment.

To further illustrate this invention. but without limit ing its scope. the following examples are given wherein parts and percentages are by weight unless otherwise indicated specifically.

4 Acid number. viscosity. color and curing effect at 80C referred to in each example were measured according to the method of JIS K690l. Stability during storage was measured. using Gbl-geltimer at l00C. To evaluate the rating of intcrcstcrification reaction. methanol tolerance at 25C was used.

EXAMPLE I A. In a 2-liter 4-necked flask equipped with a thermometer. a stirrer. a nitrogen gas inlet tube and a partial condenser tube were placed first 693 parts of dimethyl terephthalate and 275 parts of propylene glycol and then 028 part oflead acetate. 0.4 part of hydroquinone and 2.2 parts of triphenyl phosphite. While nitrogen gas was passed through the flask. the mixture placed therein was gradually heated up to 230C with stirring and maintained at this temperature to effect in tcresterif'ication reaction. When a methanol tolerance reached 2.6 (after a lapse ofabout 18 hours). the heating was stopped and the reaction product was cooled to 100C.

B. To the reaction product of stage (A) were added 567 parts of maleic anhydride. l43 parts of propylene glycol and 474 parts of dipropylene glycol. The mixture was heated to 230C to effect reaction. The progress of the reaction was checked by measurement of the acid number and viscosity of the reaction mixture. At the time the acid number became l4 and the viscosity at 30% styrene content reached 20.5 poises (after about 18 hours). the heating was stopped and the reaction product was cooled.

C. The reaction product of stage (B) was dissolved in 800 parts of styrene to produce a light yellow, transpar ent unsaturated polyester resin with the characteristic properties as shown in Table l.

The effect of using hydroquinone alone or pbenzoquinone alone in lieu of a combination of hydroquinone and triphenyl phosphite at stage (A) in this ex ample is also shown in Table l as Experiment 2 or 3. In the case of Experiment 2. gelation took place in the course of the reaction so that an unsaturated polyesterrcsin could not be obtained. In the case of Experiment 3. the product was obtained in almost gelled state with an extremely short pot life and was considerably colored so that the product was not suited for practical use.

Table l hxperimem l 2 3 Starting Dimcthyl tcrcphthalatc 693.00 693.00 (193.00 Materials Propylene glycol 175.00 275.00 275.00 at Stage Lead acetate 0.2% 0.28 0.23 (Al (pts Hydroquinonc 0.40 0.60 by weight p-Bcnyoquinone 0.60

'l'riphenyl phosphilc 2.10

Additional Malcic anhydride 567 ()0 567.00 567.00 Materials Propylene glycol 143.00 143.00 l43.00 at Slagelll) Dictliylene glycol 474.00 474.00 474.00

Monomer Styrene H00 00 s 800.00

Acld number 9.0) (iellcd 12.00 Properties \tkCUislt) (25%. poises) ll .00 49.00 olthe Rc- (olor lone (Gardner color sulting counter) 3-4 lZ-l 3 Unsaturated (icl time lmin l 4 500 Polyester (tiring lnflect Cure time lnnn l 6.50 8.00 Resin at K0C l'xothcrrn tum lBPt) paste I?! pcratnre l"(') Ill) 00 137.00

Stability on storage (hours) H00 l EXAMPLE 2 A. ln accordance with the same procedure as described in Example l. the A stage reaction was carried 6 pletely dissolved in a resin ol' Exp. 4 and the characteristics of the resin were measured. it was found that the characteristics were almost identical with those given in Table 2. Likewise. l5 parts of poly( methyl mcthac' out using 428 parts ol'dimethylterephthalate.532 parts 5 rylatc) as a low contraction-imparting agent were of propylene glycol. 0.l5 part oflead acetate. 0.40 part added to 100 parts of the resin of Exp. 4 and the charol'hydroquinone and 2.03 parts oftriphenyl phosphite acteristics of the resin were measured. Although the and finished at the time when the methanol tolerance viscosity was increased and white turbidity appeared. reached 2.5 (after a lapse of about l9 hours). no change was found in the curing effect and stability B. To the reaction product of stage (A) were added on storage. Thus. this resin seemed to be similar to a 782 parts of maleic anhydride and 301 parts of ethyllow contraction polyester resin generally employed. ene glycol. The B stage reaction was then carried out in EXAMPI E 3 the same way as described in Example 1 (B). At the time the acid number of the reaction mixture became A. ln the same way described in Example l. the A l6 and the viscosity at 307: styrene content reached stage reaction was carried out using 536 parts of di- 26.8 poises (after a lapse of about 13 hours). the heatmethyl terephthalatc. 228 parts of propylene glycol and ing was stopped and the reaction product was cooled. 0.21 part of lead acetate and concluded when a metha- C. The reaction product of stage(B) was dissolved in nol tolerance of 2.9 was obtained (after a lapse of 800 parts of styrene to produce a light yellow, transparabout l8 hours). ent unsaturated polyester resin with the characteristic B. To the reaction product of stage (A) were added properties shown in Table 2. 734 parts of maleic anhydride. 418 parts of propylene For the purpose of comparison, similar experiments glycol. 290 parts of neopentyl glycol. 0.3 part ofhydrowere repeated. using various polymerization inhibitors quinone and 2.1 parts of triphenyl phosphite. The reacsingly in place ofthc combination of hydroquinone and tion was carried out according to the procedure detriphenyl phosphite used at the A stage of this example. scribed in Example I. When the acid number of the re- Howevensatisfactory results were not obtained in all of action mixture became l7 and the viscosity of a soluthe cases. For example, when using 2,5-dition containing styrene reached 2.5 poises (after a tertbutylhydroquinone alone (Exp. 5) or a combination lapse of about 10 hours), the heating was stopped and of hydroquinone and hydroquinone dimethyl ether the reaction product was cooled. (Exp. 7) the desired result was not obtained as gelation 30 C. The reaction product of stage (B) was dissolved in took place during the B stage reaction. When using 2.5- 800 parts of styrene to produce a light yellow. transpardiphenyl-p-benzoquinone alone (Exp. 6). the B stage ent unsaturated polyester resin with the characteristic reaction could barely be finished with difficulty. Moreproperties shown in Table 3. This resin was lightly colover, the product was obtained in virtual gelled state ored but its stability on storage was good. with an extremely short pot life and considerable color- For the purpose of comparison. similar experiments ation and hence was not suitable for practical use. The were repeated. using hydroquinone or p-bcnzoquinone properties of these products are shown also in Table 2. singly. However, the product obtained was considerably colored and was hort in life and was thus of less TABLE 2 Starting Dimethyl terephthalate 423.00 428.00 428.00 428.00 Materials Propylene glycol 532.00 532.00 532.00 532.00 at Stage Lead acetate 0.l5 0.l5 0.15 0.l5 (Al lpts Hydroqu'inone 0.40 0.40 by weight] 2.5-Di-tert-butylhydroquinone 0.80 2.5-Diphenyl-p-henzoquinone 0.80 Hydroquinone dimcthyl ether 0.40 Triphenyl phosphitc 2.03

Additional Maleic anhydridc 782.00 782.00 782.00 7212.00 Materials at Stage (8] Ethylene glycol 30l.00 301.00 30l .00 30l .00

Monomer Styrene 800.00 800.00

Acid number 9.80 Gclled l I20 Gclled Viscosity (25C. poises] 28.00 37.00 Properties of Color tone (Gardner color the Resulting counter) 3-4 l3-l4 Unsaturated Gel time tr'nin.) 4.20 4.80 Polyester Curing effect (are time (min.l 6.00 7.20 Resin at C Exotherrn tem- IHPO Pthlt. W?) pcrtllurt. ("Ci 213.410 193m Stab|lity on storage (hours) 9 00 1.20

When 0.4% of an ultraviolet ray absorbing agent (Tinuvin P." a benzotriazole compound) was comcommercial value.

TABLE 3 Experiment it J l() Starting [)imethyl terephthalate 536.00 536.00 536.00 Materialat Stage Propylene glycol 22x00 228.00 228.00

TABLE 3-continucd Experiment (A) (pts Lead acetate 0,2l 0.21 0.21 by weight) Maleic anhydride 734.00 7.1400 734.00

Propylene glycol 418.00 4|K.00 418.00 Additional Materials Neopcntyl glycol 290.00 290.00 290.00 at Stage (B) Hydroquinone 0.30 0.60

p-Benzoquinonc 0 b0 Triphenyl phosphite 2.l0

Monomer Styrene 800.00 800.00 800.00

Acid number I l.00 I400 i050 Color tone (Gardner color Properties counter) 4-5 8-9 )2 -l3 of the Resulting Viscosity (C. poiscs) 20.00 28.00 26.00 Unsaturated Gel time(min.) 5.60 7.50 6.50 Polyester Curing effect Cure time (min.) 8.00 10.40 9.80 Resin at 80C Exothcrm tem (BPO paste l%) peraturc (C) l95.00 [73.00 M200 Stability on storage (hours) 9.50 0.70 0.60

What is claimed is:

l. A process for manufacturing unsaturated polyester resins which comprises (A) reacting in a first stage a dialkyl terephthalate with a polyhydric alcohol in the presence of an interesterification reaction catalyst. (B) reacting in a second stage the reaction product of stage (A) with an unsaturated dicarboxylic acid and at least one polyhydric alcohol to produce an unsaturated alkyd resin and (C) finally dissolving the unsaturated alkyd resin obtained from stage (B) in a vinyl monomer. characterized in that the reaction of stage (A) or (B) is carried out in the concurrent presence of a hydroquinone and an alkyl or aryl phosphite.

2. A process according to claim I wherein a hydroquinonc and a phosphite are present at the beginning'of stage (A).

3. A process according to claim I wherein a hydroquinone and a phosphite are present at stage (B).

4. A process according to claim 2 wherein stage (A) is carried out in the presence of hydroquinone and triphcnyl phosphite. carried 5. A process according to claim 3 wherein stage (B) is carried out in the presence of hydroquinonc and triphenyl phosphite.

6. A process according to claim 1 wherein the unsaturated dicarboxylic acid is maleic anhydride.

7. A process according to claim I wherein said stage (A) reaction product is reacted in stage (B) with a saturated dicarboxylic acid in addition to said unsaturated dicarboxylic acid and said polyhydric alcohol.

8. A process according to claim 1 wherein said hydroquinone is present in the amount of about 0.005 0.04% and said phosphite is present in the amount of about 0.005 0.5%. both by weight of the dicarboxylic acid and polyhydrie alcohol being reacted.

9. A process according to claim I where said stage (A) reaction is carried out at a temperature of about- 200250C and said stage (B) reaction is carried out at a temperature of about l230C. 

1. A PROCESS FOR MANUFACTURING UNSATURATED POLYESTER RESINS WHICH COMPRISES (A) REACTING IN A FIRST STAGE A DIALKYL TEREPHTHALATE WITH A POLYHYDRIC ALCOHOL IN THE PRESENCE OF AN INTERESTERIFICATION REACTION CATALYST, (B) REACTING IN A SECOND STAGE THE REACTION PRODUCT OF STAGE (A) WITH AN UNSATURATED DICARBOXYLIC ACID AND AT LEAST ONE POLYHYDRIC ALCOHOL TO PRODUCE AN UNSATURATED ALKYL RESIN AND (C) FINALLY DISSOLVING THE UNSATURATED ALKYL RESIN OBTAINED FROM STAGE (B) IN A VINYL MONOMER, CHARACTERIZED IN THAT THE REACTION OF STAGE (A) OR (B) IS CARRIED OUT IN THE CONCURRENT PRESENCE OF A HYDROQUINONE AND AN ALKYL OR ARYL PHOSPHITE.
 2. A process according to claim 1 wherein a hydroquinone and a phosphite are present at the beginning of stage (A).
 3. A process according to claim 1 wherein a hydroquinone and a phosphite are present at stage (B).
 4. A process according to claim 2 wherein stage (A) is carried out in the presence of hydroquinone and triphenyl phosphite. carried
 5. A process according to claim 3 wherein stage (B) is carried out in the presence of hydroquinone and triphenyl phosphite.
 6. A process according to claim 1 wherein the unsaturated dicarboxylic acid is maleic anhydride.
 7. A process according to claim 1 wherein said stage (A) reaction product is reacted in stage (B) with a saturated dicarboxylic acid in addition to said unsaturated dicarboxylic acid and said polyhydric alcohol.
 8. A process according to claim 1 wherein said hydroquinone is present in the amount of about 0.005 - 0.04% and said phosphite is present in the amount of about 0.005 - 0.5%, both by weight of the dicarboxylic acid and polyhydric alcohol being reacted.
 9. A process according to claim 1 where said stage (A) reaction is carried out at a temperature of about 200*-250*C and said stage (B) reaction is carried out at a temperature of about 180*-230*C. 